Dried/calcined sludge & residues are mixed with ashes and recycled dusts, and are smelted in a coke fired blast furnace. The blast furnace comprises a vertical, water-cooled shaft, into the top of which the silver bearing mix is charged. Slag, flux, litharge and coke are also charged with the materials. Lead, in the form of recycled litharge, is used as the metal collector to form a lead-silver alloy.

At the base of the furnace is a brick-lined removable crucible in which slag and metal alloy are continuously separated. Oxygen-enriched air is blown in close to the base of the furnace and this provides the high temperature combustion of the coke necessary for smelting. The furnace operates with the smelting zone at ~1400°C. The hot exhaust gases pass up the furnace, through the charge material and, by direct heat exchange, pre-heat the charge materials.

The furnace gases, laden with dust, fume, and moisture exit the top of the furnace and are ducted to a dry, fabric bag filter plant before discharge through a 55 metre stack to atmosphere. Metallurgical fume and dusts are removed by the filter - this method is recognised as BAT by EA. The gas stream is neutralised to avoid acidity by the lime added to the by-products of the processes.

Emissions to atmosphere are continuously monitored by a particulate monitor and the data logged onto an on-line computer. Frequent additional sampling of the exhaust stack also monitors for emissions of gaseous and fume products.

Dusts from the filter are collected into stirred mixing tanks and, by the addition of water and lime, halides are converted to soluble calcium salts. The insoluble heavy metal compounds are separated by filter press and are recycled to the blast furnace. This process is fully automated.

The solution containing the soluble salts is either discharged to drain in accordance with the requirements of our Consent to Discharge or, alternatively, it can be removed from site by tanker and treated by specialist effluent contractor to the requirements of the Environment Agency.

JBR Recovery Ltd is one of the UK and Europe's leading silver recovery and precious metal recycling specialists, offering smelting, refining and photographic waste recycling and recovery, waste incineration, waste management and Good delivery 999 refined silver.

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